subdirectories in a for loop

I'm trying to run a foor loop that opens different subfolders from a main folder. The subfolders are named "Output1", "Output2", "Output3" and so on. I want to read a file with extension .mat that contatains many variables but I need the values of a specific variable and I need to store that in a vector.

I think I am missing something in my code.

% Set the directory to search in
folder_path = 'path/to/folder';
% Get a list of all the folders in the directory
contents=dir(folder_path);
results1=[];   %vector to append the needed values

for i = 1:numel(contents)    
    directory = ['F:/PhD/Swan pruebas/Iniciados/regreso/River/MorF Rs (Veg)/Output' num2str(i) '/'];
    file_name = 'file.mat';
    file_path = [directory file_name];
    load(file_path);    
    z_i=value.z  %the value that i need
    results1=[results z_i];
end

So, from this I have two things that are not working as I expect. When I use contents it reads every file in the main folder (which are many), but I just want to read the folders that say Output and the corresponding number.

The other which is a big problem, is that the values that I am extrancting in each step of the loop are the same, so I am not sure if the code is not changing directories correctly and just reading the same file over and over, or if I'm missing a step, and I know I'm reading the same values on each step because I have plotted them each time step and are the exact same values each time. So I don't know what am I missing. Please help.

Hope I have made a clear explanation but if not, please let me know and I will try to further elaborate.

Answer 1

[Stephen23]

P = 'F:/PhD/Swan pruebas/Iniciados/regreso/River/MorF Rs (Veg)';
S = dir(fullfile(P,'Output*','file.mat'));
S = natsortfiles(S); % must be downloaded: https://www.mathworks.com/matlabcentral/fileexchange/47434-natural-order-filename-sort
for k = 1:numel(S)
    F = fullfile(S(k).folder,S(k).name);
    D = load(F, 'value');
    S(k).data = D.value.z;
end
V = [S.data]

[Contoso Donoso]

This was exaclty what I needed, thank you very much, and the natsortfiles function worked beautifuly, thanks a lot.